Rotary impact tool



Jan. 11, 1966 F. A. KAMAN ETAL 3,228,486

ROTARY IMPACT TOOL Filed Sept. 11, 1962 3 Sheets-Sheet 1 NVENTORS frarz/adfiafizczrz, ZZwsr [5t harm,

BY Carl J fiherz eZ, MM fl Jan. 11, 1966 F. A. KAMAN ETAL ROTARY IMPACT TOOL 3 Sheets-Sheet 5 Filed Sept. 11, 1962 INVENTORQS- fZcZWZcZfL,

Fran/z 4 n I 1 M w Z a? United States Patent 3,228,486 ROTARY IIVIPACT TOOL Frank A. Kaman, Prospect Heights, Carl J. Frenzel, Chicago, and Elmer F. Etzkorn, Park Ridge, 111., assignors to Skil Corporation, Chicago, a corporation of Delaware Filed Sept. 11, 1962, Ser. No. 222,868 9 Claims. (Cl. 173-936) The present invention relates to rotary impact tools and, more particularly, to improvements in a rotary impact mechanism for such tools.

An important object of the invention is to provide a new and improved portable reversible rotary impact tool wherein a rotatably mounted anvil having tool mounting means on the forward end thereof is provided with rotary impact blows by a rotatably driven hammer once during each revolution of the hammer.

Another important object of the invention is to provide a new and improved portable reversible rotary impact tool wherein the rotary hammer is driven by a rotary air motor and wherein the rotary hammer is adapted to rebound through a partial revolution after delivering each impact blow whereby the air motor is allowed to accelerate through one revolution plus the amount of rebound for increasing the degree of impact delivered to the rotatably mounted anvil.

A more detailed object of the present invention is to provide a new and improved rotary impact tool of the character described wherein the hammer is provided with a pair of jaw members at its forward end which are pro jected forwardly once during each revolution of the hamrner whereby to deliver impact blows to the sides of radially extending arms formed on the anvil immediately forward of the end of the hammer.

Another important object of the invention is to provide a new and improved reversible rotary impact tool of the character described wherein a novel arrangement of three cam plate members is provided for projecting the jaw members of the hammer forwardly into their positions for delivering impact blows to the anvil with the cam plate members co-acting in one manner during rotation of the hammer in one direction and in another manner during rotation of the hammer in the opposite direction.

Another important object of the invention is to provide a new and improved rotary impact tool of the character described wherein the rotary hammer is driven by rotary accelerating means and wherein the jaw members of the hammer are positively positioned by the cam plates for impact engagement with the anvil whereby to provide an efiicient transfer of energy from the hammer to the anvil and a high energy impact thereon.

Another important object of thepresent invention is to provide a new and improved portable rotary impact tool of the character described which provides a single balanced blow per revolution of the hammer whereby to provide durability of the tool and comfort of operation thereof.

Certain other objects of the invention will, in part, be obvious, and will in part appear hereinafter.

For a more complete understanding of the nature and scope of the invention reference may now be had to the accompanying drawings wherein:

FIG. 1 is a generally vertical central section taken through a portable rotary impact tool embodying the invention with the jaw members of the hammer being in the forwardly projected positions for delivering impact blows to side edges of the radial arms of the anvil during clockwise rotation of the hammer as viewed from the handle end of the tool;

FIG. 2 is a front end view of the anvil as positioned 3,223,486 Patented Jan. 11, 1966 in FIG. 1 with the jaw members of the hammer being shown in broken line;

FIG. 3 is a vertical section taken generally on the line 3-3 of FIG. 1 illustrating the arrangement of ramp-like cam members on the front face of the rearwardmost cam plate;

FIG. 4 is a vertical section taken generally on the line 44 of FIG. 1 illustrating the arrangement of ramp-like cam members on the rear face of the intermediate cam plate;

FIG. 5 is a vertical section taken generally on the line 55 of FIG. 1 illustrating the arrangement of ramp-like cam members on the front face of the intermediate cam plate;

FIG. 6 is a vertical section taken generally on the line 66 of FIG. 1 illustrating the arrangement of ramp-like cam members on the rear face of the forwardmost cam plate;

FIGS. 7-10 each includes a series of three views illustrating operation of the impact mechanism of the tool of FIG. 1 during clockwise rotation of the hammer as viewed from the handle end of the tool with FIGS. 7-1O each including a graphic vertical section of the impact mechanism and top and bottom plan views thereof and with the views of FIGS. 7-10 illustrating, respectively, the start of the clockwise impact cycle, the point at which the jaws of the hammer are about to be projected forwardly for impact engagement with the anvil, the point of impact of the jaws of the hammer with the anvil, and the rebound of the hammer after delivery of the impact blow to the anvil; in each of the vertical sections of FIGS. 7-10, the forward face of the intermediate cam plate and the rear face of the forwardmost cam plate have been rotated approximately (in a counterclockwise direction as viewed in the top plan View of these figures) from their true position for purposes of illustration; and

FIGS. 11-14 each includes a series of three views illustrating operation of the impact mechanism of the tool of FIG. 1 during counterclockwise rotation of the hammer as viewed from the handle end of the tool'with FIGS. 1114 each including a graphic vertical section of the impact mechanism and top and bottom plan views thereof and with the views of FIGS. 1l-14 illustrating, respectively, the start of the counterclockwise impact cycle, the point at which the jaws of the hammer are about to be projected forwardly for impact engagement with the anvil, the point of impact of the jaws of the hammer with the anvil, and the rebound of the hammer after delivery of the impact blow of the anvil; in each of the vertical sections of FIGS. ll-l4, the forward face of the intermediate cam plate and the rear face of the forward most cam plate have been rotated approximately 90 (in a clockwise direction as viewed from the top plan views of these figures) from their true position for purposes of illustration.

As illustrated in FIG. 1, a portable rotary impact tool 20 embodying the invention includes a housing structure 21 characterized by a forwardly projecting barrel por tion 22 and by a rearwardly disposed depending handgrip portion 23. A rotary accelerating device, such as an air motor 24 of known type shown in FIG. 1, is provided in the rear end of the barrel housing portion 22. As illustrated, the air motor 24 includes a fixedly mounted stator structure 25 and a rotor element 26 which extends therethrough and has a series of vanes 27 associated therewith. The rotor element 26 is rotatably supported in the stator structure 25 in ball bearings 28 and 29, respectively. The forward end of the rotor element 26 is provided with a spline formation 30 for driving engagement with the rotary impact mechanism to be described herein. Whatever known type of rotary accelerating device is utilized in the rotary impact tool 20, it should preferably be a hightorque low inertia type device whereby to provide high acceleration characteristics for rotatably driving the impact mechanism to be described.

When air under pressure is directed to the air motor 24 the rotor element 26 thereof will be rotatably driven in a manner well known in the art. A reversing valve member 32, which is manually shiftable transversely of the rotary impact tool 20 between two operable positions, is adapted in one position to direct air under pressure to the air motor 24 in a manner whereby the rotor element 26 will be rotated in a clockwise direction, as viewed from the rear of the tool 20, and in its other position to direct air under pressure to the air motor 24 in a manner whereby the rotor element 26 will be rotated in a counterclockwise direction, as viewed from the rear of the impact tool 20.

Air under pressure is directed to the reversing valve 32 through a series of passages, chambers and valves provided in the handgrip portion 23 of the housing structure 21. In the rotary impact tool 20 illustrated in FIG. 1, an air pressure line or conduit is adapted to be connected to an air inlet connector 34 having an air filter element 36 associated therewith. After passing through the air filter element 36, the air under pressure is directed through a passage 37 into a chamber 38. A passage 40 leads from the chamber 38 into a chamber 41. The entrance end of the passage 40 is controlled by a valve member 39 in the chamber 38, which valve member is opened by the tool operator prior to commencing an operation with the tool 20 whereby to permit the air under pressure to be directed into the chamber 41 which is normally closed by a plungertype valve 42 of known type. The valve 42, which is normally retained in its closed position by a spring mernber 44, may be readily opened by pressing inwardly on a depressible plunger head 46 which projects forwardly from the front surface of the handgrip housing portion 23, whereby to permit the air under pressure to pass from the chamber 41 into a passage 47 and then into a chamber 49 which is in communication with the reversing valve 32. The plunger head 46 of the valve 42 is positioned for convenient engagement by a persons index or trigger finger as the handgrip housing portion 23 of the tool 20 is held normally in the hand.

The invention is primarily concerned with the novel rotary impact mechanism of the rotary impact tool 20. Briefly, the impact mechanism includes a hammer structure 52 which is adapted to be rotatably driven by the rotary accelerating device 24, a tool supporting anvil 54 which is adapted to have a rotary impact blow imparted thereto by the hammer structure 52 once during each revolution of the hammer structure 52, and a series of cam plates operably disposed between the hammer structure 52 and the anvil 54.

The hammer structure 52 which is rotatably mounted in the forwardly projecting barrel portion 22 of the housing structure 21 is generally cylindrical and may be formed of front and rear portions secured together as illustrated in the drawings. The rearwardmost end of the hammer structure 52 is provided with a reduced-in-diameter neck portion 57 having an inner spline formation 58 adapted for rotatable driving engagement with the spline formation 30 provided on the forward end of the rotor element 26 of the air motor 24. The reduced-in-diameter neck portion 57 of the hammer structure 52 is rotatably supported in ball bearings 59.

A pair of cylindrical jaw or impact members 61, made of hardened steel in the form of pins, are mounted in a pair of bores 62 formed in the front end of the hammer structure 52 in diametrically opposite relationship to the axis of rotation thereof with the jaw members 61 being movable in the bores 62 forwardly and rearwardly of the hammer structure 52. Rearwardly of the front face of the hammer structure 52, the bores 62 are increased slightly in diameter, as at 63 in FIG. 1, whereby to accgmmodate slightly increased-in-diameter rear end portions 64 of the jaw or impact members 61. Rearwardly facing shoulders 65 (FIG. 1) are defined between the bore portions 62 and 63. A pair of springs 66 are disposed one about each of the jaw members 61, which springs 66 are seated between the shoulders 65 and the increased-indiameter rear end portions 64 of the jaw members 61 whereby to normally urge the jaw members 61 into rearwardmost positions wherein the front ends thereof are disposed slightly rearwardly of the front face of the hammer structure 52.

As is illustrated in FIG. 1, the anvil 54, which is generally elongated, is rotatably mounted by means of roller bearings 68 in a sleeve member 69 secured in a cylindrical bore 70 provided in the front end of the forwardly extending barrel portion 22 of the housing structure 21 in axial alignment with the axis of rotation of the rotor element 26 of the air motor 24. The anvil 54 is characterized by a front end portion 72 which projects forwardly of the housing structure 21 and has a configuration for non-rotatably supporting a suitable tool element thereon and by a rearwardly extending shank portion 74 which extends axially through the hammer structure 52 into close proximity with the forward end of the rotor element 26. It is noted that there is no direct operable connection between the shank portion 74 of the anvil 54 and the rotor element 26. The anvil 54 and the hammer structure 52 are rotatable relative to each other and roller bearings 76 (FIG. 1) are provided therebetween. The anvil 54 is further characterized by a pair of integral diametrically opposite radially extending arms 78 which are disposed closely adjacent to the front face of the hammer structure 52. During rotation of the hammer structure 52, provision is made for projecting the jaw or impact members 61 forwardly from their normally retracted positions whereby the jaw members 61 impart rotary impact blows to corresponding side edges of the anvil arms 78 depending upon the direction of rotation of the hammer structure 52. As best illustrated in FIG. 2, the side edges of the anvil arms 78 are provided with arcuate depressions 80 which are adapted to accommodate the jaw or impact members 61 at the point of impact therebetween.

During rotation of the hammer structure 52 in either direction, a single rotary impact blow is imparted to the anvil 54 once during each revolution of the hammer structure 52. This impact blow is a balanced one inasmuch as corresponding side edges of the anvil arms 78 are struck simultaneously by the pair of jaw or impact members 61. This balanced impact blow lends itself to ease and comfort of operation for the tool operator and substantially reduces the stress and strain on the elements of the rotary impact mechanism whereby to substantially improve the durability thereof.

After each impact of the jaw members 61 of the hammer structure 52 with the anvil arms 73, the hammer structure 52 will rebound varying degrees in accordance with the resistance encountered by the tool element mounted on the forward end 72 of the anvil 54. Thus, after each impact blow, the rotary elements of the low inertia air motor 24 are rotatable through more than a full revolution before the next impact blow whereby to increase the acceleration attained by the hammer structure 52 and thus provide for a high energy impact blow to be imparted to the anvil 54. Obviously, it is important that the jaw or impact members 61 be retracted immediately after delivery of the impact blow to the anvil arms 78 whereby to prevent possible interference be tween the anvil arms 78 and the jaw members 61 on the hammer structure 52 during both the rebounding move ment of the hammer structure 52 and during the next forward acceleration rotation of the hammer structure 52 prior to forward projection of the jaw members 61 for delivery of the neXt impact blow to the anvil arms 7 8.,

The previously mentioned series of earn plates serves,

during rotation of the hammer structure 52 in either direction, to project the jaw members 61 forwardly at the proper moments for imparting impact blows to the anvil arms 78 and also to permit immediate reaction of the jaw members 61 after delivery of the impact blows. This series of cam plates, each of which is generally circular, includes a forwardmost plate 82 (FIG. 6), an intermediate or spacer plate 84 (FIGS. 4 and 5), and a rear wardmost plate 86 (FIG. 3).

The forwardmost calm plate 82, which is centrally bored, is fitted over the shank portion 74 of the anvil 54 for rotational and limited axial movements relative thereto. The cam plate 82 is further characterized by a pair of diametrically opposite outwardly projecting radial flanges 88 which are received in longitudinally extending mating recesses (not shown) provided in the hammer structure 52 whereby to effectively key the forwardmost cam plate 82 to the hammer structure 52 for rotation therewith. The radial flanges 88 of the cam plate 82 extend over a substantial portion of the rear end surfaces of the jaw or impact members 61 whereby to retain the jaw members 61 in the bores 62 despite the rearward resilient forces exerted on the jaw members 61 by the springs 66. Axial movement of the cam plate 82 in a forward or outward direction serves to project the jaw or impact members 61 forwardly into their positions for impact engagement with the anvil arms 78. The rear face of the forwardmost cam plate 82 is provided with a pair of diametrically opposite arcuately extending integral ramp-like cam members 90 and 91. The cam members 90 and 91 are disposed in radially spaced relationship on the rear face of the cam plate 82 with the outer cam member 90 being disposed along the outer edge of the cam plate 82 and the inner cam member 91 being disposed along the inner edge thereof. As most clearly illustrated in FIG. 6, the cam members 90 and 91 are provided, respectively, with inclined ramp surfaces 90a and 91a, relatively short planar surfaces 90b and 91b spaced from the rear surface of the cam plate 82 and extending parallel thereto, and flat end surfaces 90c and 91c disposed at right angles to the rear surface of the cam plate 82. The rear face of the cam plate 82 is also provided with diametrically opposite shallow depressions or recesses 90d and 91d. These depressions are disposed in radially spaced relationship with the outer depression 90d being disposed along the outer edge of the cam plate 82 and the inner depression 91d being disposed along the inner edge thereof. The real face of the forwardmost cam plate also includes a second set of diametrically opposite shallow depressions or recesses 90e and 91e. In like manner these depressions are disposed in radially spaced relationship with the outer depression 90e being disposed along outer edge of the plate 82 and the inner depression 91e being disposed along the inner edge thereof. It will be noted that the depressions 90e and 91s are angularly spaced, i.e., proceeding in a clockwise direction as viewed in FIGURE 6, about 225 from the depressions 90d and 91d.

The intermediate or spacer cam plate 84, which is centrally bored, is mounted on the shank portion 74 of the anvil 54 rearwardly of the forewardmost cam plate 82 for rotational and limited axial movement relative thereto. The front face of the intermediate cam plate 84 (FIG. 5) is provided with a pair of diametrically opposite arcuately extending integral ramp-like cam members 92 and 93. The cam members 92 and 93 are disposed in radially spaced arrangement on the front face of the cam plate 84 with the outer cam member 92 being disposed along the outer edge of the cam plate 84 and the inner cam member 93 being arranged along the inner edge thereof. As most clearly illustrated in FIG. 5, the cam members 92 and 93 are characterized, respectively, by inclined ramp surfaces 92a and 93a, relatively short planar surfaces 92b and 93b spaced from the front face of the cam plate 84 and extending parallel thereto, and flat end surfaces 92c and 930 disposed at right angles to the front face of the cam plate 84. The flat end surfaces 92c and 93c of the cam members 92 and 93 face in opposite rotational directions than the flat end surfaces 900 and 910 of the cam members and 91 on the forwardmost cam plate 82 for purposes that will be explained hereinafter. The front face of the intermediate cam plate 84 is also provided with a pair of diametrically opposite shallow depressions 92d and 93a. The outer depression 92d is disposed along the outer edge of the plate 84 and the depression 93d is disposed along the inner edge thereof. A second set of diametrically opposite shallow depressions or recesses 92a and 93s are formed on the front face of the cam plate 84. In like manner these depressions are disposed in radially spaced relationship with the outer depression 92c being disposed along the outer edge of the plate 82 and the inner depression 93:? being disposed along the inner edge thereof. Again, it will be noted that the shallow depressions 92c and 930 are angularly spaced, i.e., in a clockwise direction as viewed in FIGURE 5, approximately 225 from the oppositely disposed depressions 92d and 93d.

The rear face of the intermediate cam plate 84 (FIG. 4) is provided with a pair of diametrically opposite arcurately extending integral ramplike cam members 94 and 95. The cam members 94 and 95 are disposed in radially spaced relationship on the rear face of the cam plate 84 with the outer cam member 94 being disposed along the outer edge of the cam plate 84 and the inner cam member 95 being disposed along the inner edge thereof. The cam members 94 and 95 are angularly spaced approximately 90, respectively, from the cam members 92 and 93 on the front face of the cam plate 84. That is, as viewed in FIG. 5 of the drawings, cam members 94 and 95 are angularly spaced 90 in a clockwise direction from respective cam members 92 and 93. As most clearly illustrated in FIG. 4, the cam plates 94 and 95 are characterized, respectively, by inclined ramp surfaces 94:: and 95a, relatively short planar surfaces 94b and 95b spaced rearwardly of the rear face of the cam plate 84 and extending parallel thereto, and flat end surfaces 940 and 950 disposed at right angles to the rear face of the cam plate 84. The fiat end surfaces 940 and 950 of the cam members 94 and 95 face in the same rotational direction as the fiat end surfaces 920 and 93c of the cam members 92 and 93 on the front face of the intermediate cam plate 84.

The rearwardmost cam plate 86, which is centrally bored, is fitted over the shank portion 74 of the anvil 54 rearwardly of the intermediate cam plate 84. The rear face of the rearwardmost cam plate 86 (see any of the top plan views in FIGS. '7-14) is provided with a pair of diametrically opposite sector-shaped recesses 96 which intersect the central bore formed in the cam plate 86 with the angle determined between the opposite ends of each of the sector-shaped recesses 96 being in the order of 90. The rearwardmost cam plate 86 is operably connected to the shank portion 74 of the anvil 54 by a pin 97 which extends through a radially extending bore formed in the end of the shank portion 74 with the ends of the pin 97 being received in the two sector-shaped recesses 96. The rearward resilient force exerted by the spring members 66 on the jaw or impact members 61 is transmitted through the forwardmost cam plate 82 and th intermediate cam plate 84 to the rearwardmost cam plate 86 whereby the pin 97 is resiliently retained within the confines of the sector-shaped recesses 96. To prevent momentary forward movement of the rearwardmost cam 86 during operation of the tool, which might result in separation of the pin 97 from the shank 74, the shank 74 is provided with an annular groove 97a adapted to receive a C-ring 97b which ring is adapted to abut the front face of the cam 86. In this way axial movement of the cam 86 with respect to the shank 74 is precluded. With the foregoing structural arrangement, the rearwardmost cam plate 86 is rotatable relative to the shank portion 74 of the anvil 54 7 with such relative rotation being limited to approximately 90.

The front face of the rearwardmost cam plate 86 is provided with a pair of diametrically opposite arcuately extending integral ramp-like cam members 98 and 99. The cam members 98 and 99 are disposed in radially spaced arrangement on the front face of the cam plate 86 with the outer cam member 98 being disposed along the outer edge of the cam plate 86 and the inner cam member 99 being disposed along the inner edge thereof. As most clearly illustrated in FIG. 3, the cam members 98 and 99 are characterized, respectively, by inclined ramp surfaces 98a and 99a, relatively short planar surfaces 98b and 99b spaced forwardly of the front face of the cam plate 86 and extending parallel thereto, and flat end surfaces 980 and 990 disposed at right angles to the front face of the cam plate 86. The end surfaces 98c and 990 of the cam members 98 and 99 face in opposite rotational directions than the flat end surfaces 940 and 950 of the cam members 94 and 95 on the rear face of the intermediate cam plate 84.

It will be noted that all cam members have the same shape and differ only in arcuate length depending on their distance from the center of rotation of the cam plates. That is, each cam member includes an inclined arcuate surface which rises from the face of the associated cam plate and which terminates or joins at its high point, i.e. its planar surface, with an end surface which is normal with the face of the associated cam plate. As will become apparent from the following description of the operation of the impact mechanism, because of this shape of the cam members, after the cam members, which move the cam plate or plates forwardly, clear each other the cam plate or plates so moved may be immediately moved rearwardly after an impact blow is delivered to the anvil arms. This arrangement permits the jaws to be retracted almost immediately after impact thereby to prevent the jaws from contacting the anvil arms before the hammer has accelerated through at least another full revolution.

For proper operation of the rotary impact mechanism of the rotary impact tool 20, the outer cam members 90, 92, 94 and 98 should be substantially identical dimensionwise and formwise whereby the opposing inclined cam surfaces 90a92a and 9411-9811 thereof will be complementary. Likewise, the inner cam members 91, 93, 95 and 99 should be substantially identical dimensionwise and formwise whereby the opposing inclined cam surfaces 91a-93a and 95a-99a thereof will be complementary. The planar surfaces 90b, 91b, 92b, 93b, 94b, 95b, 98b and 99b of all the cam members are preferably spaced equal distances from their respective cam plates. The arcuate length of the outer cam members 90, 92, 94 and 98 is somewhat greater than the arcuate length of the inner cam members 91, 93, 95 and 99 as the outer cam members are spaced a greater radial distance from the axis of rotation of their respective cam plates than are the inner cam members. The radial dimensions and positioning of the inner and outer cam members is such that there will be no interference between the outer cam member on one cam plate and an inner cam member on an adjacent cam plate during relative rotation of the cam plates.

As will be fully explained, the three cam plates 82, 84 and 86 co-act in one manner during rotation of the hammer structure 52 in one direction to project the jaw or impact members 61 forwardly into their positions for imparting impact blows to corresponding side edges of the anvil arms 78 and in a different manner during rotation of the hammer structure 52 in the opposite direction to project the jaw or impact members 61 into their forwardmost positions for imparting impact blows to the opposite side edges of the anvil arms 78.

Operation of the rotary impact mechanism during rotationof the hammer structure 52 by the air motor 24 in a clockwise direction (as viewed from the rear or hand grip end of the rotary impact tool 20 illustrated in FIG. 1) may best be described with reference to FIGS. 7, 8, 9 and 10. As mentioned above in connection with the description of the drawings, in FIGS. 714, the rearwardmost cam 86 and the rear face of the intermediate cam 84 have been rotated approximately 90 to better show the operation of the cams. In the following discussion, the term clockwise will refer to the direction of rotation of the various parts as viewed from the rear of the rotary impact tool 20 shown in FIG. 1. In FIG. 7, which illustrates graphically the various elements of the rotary impact mechanism during the beginning of a forward rotary impact cycle, the forwardmost cam plate 82 is rotated in a clockwise direction with the hammer structure 52 with the fiat end surfaces 90c and 910 of the cam members 90 and 91 thereon engaging the flat end surfaces 920 and 93c, respectively, of the cam members 92 and 93 on the forward or outer face of the intermediate cam plate 84 whereby to rotate the intermediate cam plate 84 in a clockwise direction, the forwardmost and intermediate cam plates 82 and 84 being in effect operably keyed together. When the cam plates 82 and 84 are in this position relative to each other the planar surfaces 9% and 91b on the cam 82 Will be receive-d in the shallow depressions 92d and 93d, respectively, in the front face of the intermediate cam 84. It is noted that clockwise rotation of the rearwardmost cam plate 86 is prevented (when the anvil resists rotation as when a nut being run begins to seat or otherwise resist rotation) by engagement of corresponding ends of the sector-shaped recesses 96 therein against opposite ends of the pin 97 extending through the shank portion 74 of the anvil 54.

After the hammer structure 52 and the forwardmost and intermediate cam plates 82 and 84 have been rotated approximately 300 in a clockwise direction to the positions indicated in FIG. 8, the inclined cam surfaces 94a and a of the cam members 94 and 95 on the rear or inner face of the intermediate cam plate 84 complementarily engage, respectively, the inclined cam surfaces 98a and 99a of the cam members 98 and 99 on the front or outer face of the rearwardmost cam plate 86. During run-up of a nut, the various cams remain in the positions illustrated in FIG. 8. When the rearwardmost cam plate 86 is prevented from turning by the anvil, continued clockwise rotation of the hammer structure 52 and the forwardmost and intermediate cam plates 82 and 8 relative to the rearwardmost cam plate 86 through approximately 45 to the positions indicated in FIG. 9, the complementary inclined cam surfaces 94a-98a and 95a 99a ride-up on or co-act with each other whereby to cam both the forwardmost and intermediate cam plates 82 and 84 forwardly or outwardly to project the jaw or impact members 61 into their positions for delivering rotary impact blows to corresponding side edges of the anvil arms 78 in a clockwise direction. As it will be noted from FIG. 9 which shows the jaws 61 delivering their impact blow to the anvil 54 the planar surface 98b of the cam 86 has separated from the planar surface 94b of the intermediate cam 84. The condition of the rotary impact mechanism illustrated in FIG. 9 is also illustrated in FIG. 1 and the related views of FIGS. 2-6.

Immediately after or simultaneously as the rotary impact blows are delivered, the engaged planar cam surfaces 94b-98b and 95b99b clear each other whereby to permit immediate and rapid retraction of the jaw members at by the springs 65. As a result of the impact blows delivered by the jaws 61 to the anvil arms '78, the hammer structure 52 and the forwardmost cam plate 82 keyed thereto rebound in a counterclockwise direction as indicated in FIG. 10. In FIG. 10 it will be noted that the cam end surfaces 90c and 920 are shown separated during the period of rebound. It is desirable to limit as much as possible relative movement between the cams 82 and 84 during rebound to prevent undue wear on these cams. It has been found that the shallow depressions 93d, 91d, 92d and 93d which are adapted to receive the planar surfaces 92b, 93b, 9% and 91b, respectively, contribute materially to the prevention of relative movement between the forwardmost and intermediate cam. However, if during the period of rebound the cams 82 and 8d rotate relative to each other, they will be prevented from oppositely rotating to a degree where the respective inclined cam surfaces thereon would tend to contact each other. After the two cams have rotated relative to each other for approximately 225, the planar surfaces of the respective cams will slide into the second set of depressions in the cam members tending to prevent further relative movement between the cams 82 and 84. That is, the planar surfaces 90b and 91b of the cam 82 would be received in the depressions 92c and 932, respectively, of the cam 84 while the planar surfaces 92b and 93b of the cam 84 would be received in the depressions 902 and 912, respectively, of the cam 82. The provision of all of these depressions in the cam faces has been found to reduce relative movement between these two cam plates during the period of rebound thereby tending to prolong the life of these parts. It will also be realized that during the period of rebound the rearwardmost cam may rotate for approximately 90 with respect to the shank 74, i.e., the cam 86 may rotate until the other end of each of the sector-shaped recesses 96 is contacted by the projecting ends of the pin 97. The degree of rebound will vary in accordance with the resistance to rotary movement encountered by a tool element supported on the forward end portion 72 of the anvil 54. Before the next and each succeeding impact blow is imparted by the jaw or impact members 61, the hammer structure 52 will therefore rotate an angular distance greater than one full 360 revolution depending upon the degree of rebound of the hammer structure 52 as a result of the last or preceding impact blow. This increased degree of rotation permitted the hammer structure 52 allows the low inertia accelerating device (the air motor 24 in the embodiment illustrated in FIG. 1) to develop a substantially high degree of acceleration for the hammer structure 52, whereby to provide high energy impact blows by the jaw or impact members 61 to the anvil arms '78.

Operation of the rotary impact mechanism during rotation of the hammer structure 52 in a counterclockwise direction (as viewed from the rear or hand grip end of the rotary impact tool 26 illustrated in FIG. 1) may best be escribed with reference to FIGS. 11-14. As will be noted, the cam plates 82, 84 and 86 co-act in a different manner than during rotation of the hammer structure in a clockwise direction.

As illustrated in FIG. 11, during the beginning of a counterclockwise or reverse impact cycle, the forwardmost cam plate 82 is rotated in a counterclockwise direction with the hammer structure 52. During this counterclockwise rotation of the forwardmost cam plate 82, the intermediate cam plate 84 is held against counterclockwise rotation as a result of engagement of the fiat end surfaces 940 and 950 of the cam members 94 and 95 on the rear or inner face of the intermediate cam plate 84, respectively, with the fiat end surfaces 98c and 990 of the cam members 98 and 99 on the front or outer face of the rearwardmost cam plate 86, the rearwardmost cam plate 86 being held against counterclockwise rotation as a result of engagement of corresponding ends of the sector-shaped recesses 96 with opposite ends of the pin 97 extending through the shank 74 of the anvil 54, the intermediate and rearwardmost cam plates 84 and 86 being in effect operably keyed together. It is noted that during counterclockwise rotation of the hammer structure 52 the pin 96 is engaged with opposite ends of the sector shaped recesses 96 than those ends thereof engaged by the pin 97 during clockwise rotation of the hammer structure 52.

After the hammer structure 52 and the forwardmost cam plate 82 have rotated approximately 300 in a counterclockwise direction to the positions indicated graphically in FIG. 12, the inclined cam surfaces a and 91a of the cam members 90 and 91 on the rear or inner face of the forwardmost cam plate 82 complementarily engage, respectively, the inclined cam surfaces 92a and 3a of the cam members 92 and 93 on the front or outer face of the intermediate cam plate 84 which is held stationary as a result of its engagement with the rearwardmost cam plate 86 (assuming cam plate 86 is prevented from turning by resistance to rotation of the anvil). During run-up of a nut being run, ie when the anvil does not resist rotation and when there is no relative rotation between the hammer and the anvil, the various cam plates remain in their positions illustrated in FIG. 12. During continued counterclockwise rotation of the hammer structure 52 (relative to the anvil) and corresponding rotation of the forwardmost cam plate 82 relative to the stationarily held intermediate cam plate 84 through approximately 45 to the positions indicated in FIG. 13, the complementary inclined cam surfaces 90a-92a and 91a-93a ride-up on or co-act with each other whereby the forwardmost cam plate 82 is cammed forwardly or outwardly to project the jaw or impact members 61 into their positions for delivering impact blows to the opposite side edges of the anvil arms 78 in a counterclockwise direction.

Immediately after or simultaneously as the rotary impact blows are delivered in a counterclockwise direction, the engaged planar cam surfaces 90b-92b and 91b-93b clear each other whereby to permit immediate and rapid retraction of the jaw members 61 by the springs 66. As a result of the counterclockwise impact blows delivered by the jaw or impact members 61 to the anvil arms 78, the hammer structure 52 and the forwardmost and intermediate cam plates 82 and 84 rebound in a clockwise direction, as indicated in FIG. 14. During rebound when the tool is operating in a counterclockwise direction the situation of relative movement between the cams 84 and 86 is not the same as relative movement of the cams 82 and 84 during clockwise operation of the tool, since during counterclockwise operation it is the cam 82 keyed to the hammer structure 52 which tends to rebound and not the cam 86. Accordingly, shallow depressions or recesses have not been provided on mating faces of the cam plates 84 and 86. As previously noted, the degree of rebound will vary in accordance with the resistance to rotary movement encountered by a tool element supported on the forward end portion 72 of the anvil 54. Thus, as previously set forth herein, before the next and each succeeding counte rclockwise impact blows are imparted by the jaw or impact members 61 to the anvil 54, the hammer structure 52 will rotate an angular distance in a counterclockwise direction greater than one full 360 revolution depending upon the degree of clockwise rebound of the hammer structure 52 as a result of the last or preceding impact blow. Again, this increased degree of rotation permitted the hammer structure 52 allows the low inertia accelerating device (the air motor 24 in the embodiment illustrated in FIG. 1) to develop a substantially high degree of acceleration for the hammer structure 52 whereby to provide high energy impact blows by the jaw members 61 to the anvil arms 7 8.

As the jaw or impact members 61 are retracted immediately after each impact blow, during either clockwise or counterclockwise rotation of the hammer structure 52, there will be no interference with rebound movement of the hammer structure 52 by the anvil arms 78 should the hammer structure 52 rebound as much as approximately 60". Likewise, during the next accelerating revolution of the hammer structure 52 through 360 or more in preparation for the next impact blow, there will be no interference with the accelerating movement of the hammer structure 52 by the anvil arms 7 8 until the jaw or impact 11 members 61 are again projected forwardly or outwardly to deliver the next impact blows to the anvil arms '78.

With the rotary impact mechanism disclosed herein, during rotation of the hammer structure 52 in a clockwise direction, in the embodiment illustrated and described herein, the forwardmost and intermediate cam plates 82 and 84, respectively, are both automatically shifted forwardly whereby to project the jaw or impact members 61 into their positions for delivering rotary impact blows to corresponding sides of the anvil arms '78 and during rotation of the hammer structure 52 in a counterclockwise direction, the forwardmost cam plate 82 is automatically shifted forwardly whereby to project the jaw or impact members 61 into their positions for imparting rotary impact blows to the opposite side edges of the anvil arms 78.

To insure forward or outward projection of the jaw or impact members 61 at the proper moments for imparting impact blows to the proper sides of the anvil arms 78 during clockwise and counterclockwise rotation of the hammer structure 52, the following angular relationship between certain of the elements of the rotary impact mechanism described herein are preferred. As best illustrated in FIG. 6, the cam members 90 and 91 on the forwardmost cam plate 82 are arranged in generally centered radial alignment with the radial flanges 88 thereof. As best illustrated in FIG. 3, the cam members 98 and 99 on the front or outer face of the rearwardmost cam plate 86 are angularly located thereon between the pair of sector-shaped recesses 96 formed in the rear or inner face of the rearwardmost cam plate 86. The pin 97 extends through the shank portion 74 of the anvil 54 at approximately right angles to the radially extending anvil arms 78. As previously stated herein, the cam members 94 and 95 on the rear or inner face of the intermediate cam plate 84 are angularly spaced approximately 90 from the cam members 92 and 93, respectively, provided on the front or outer face of the intermediate cam plate 84. These various relationships, which are shown for purposes of illustration, provide for the jaws being cammed forwardly at the proper time in advance of reaching the anvil arm for delivering impact blows to the latter.

It is noted that there is positive engagement between coacting elements of the rotary impact mechanism of the rotary impact tool 2% described and illustrated herein whereby to provide an efiicient transfer of energy between the various elements of the impact mechanism and thus high energy impact blows from the jaw members 61 of the hammer structure 52 to the anvil 54. To be more specific, it is noted that the hammer structure 52 is positively driven by the rotor element 26 of the air motor 24 and that the cam plates 82, 84 and 86 are positively rotated and axially shifted whereby to positively project the jaw or impact members 61 into their forwardmost positions for delivering high energy impact blows to the anvil arms '78. It is further noted that numerous sealing gaskets of known types may be provided as needed in the rotary impact tool 20. Such sealing gaskets have not been identified and described in detail inasmuch as they comprise no part of the invention.

It will be understood that certain changes may be made in the construction or arrangement of the rotary impact tool disclosed herein without departing from the spirit and scope of the invention as defined in the appended claims.

We claim:

1. In a rotary impact tool of the type having a generally cylindrical hammer adapted to be rotatably driven by reversible rotary accelerating means, an elongated anvil including a shank portion extending co-axially through said hammer and being rotatable relative thereto, which anvil is characterized by a pair of diametrically opposite radially extending arms disposed adjacent to the front surface of said hammer and which hammer is characterized by a pair of diametrically opposite jaw members slidably mounted in its front end and normally spring urged to positions rearwardly of the front surface of the hammer,

means for projecting said jaw members forwardly once during each revolution of the hammer relative to the anvil whereby to deliver impact blows to said anvil arms comprising, a plate member rotatably mounted on the shank portion of said anvil member and keyed to said hammer for rotation therewith, said plate member having its forward face engageable with the rear ends of said pair of jaw members and being mounted for movement axially of said hammer and said anvil member, and cam means rotatable with and relative to said hammer for shifting said piate member forwardly whereby to project said jaw members forwardly into positions for delivering impact blows to said anvil arms once during each revolution of said hammer, said cam means including first and second cooperating cams each of which includes a ramp surface and an end surface extending axially of the hammer allowing said plate member to be shifted rearwardly immediately after said cams pass each other thereby permitting immediate retraction of said jaw members by said spring means upon delivery of said blows whereby to prevent interference between said jaw members and said anvil arms during rebound of said hammer and during the next revolution of said hammer until said plate member is again shifted forwardly by said cam means.

2. In a rotary impact tool of the type having a generally cylindrical hammer adapted to be rotatably driven by reversible rotary accelerating means, an elongated anvil including a shank portion extending co-axially through said hammer and being rotatable relative thereto, which anvil is characterized by a pair of diametrically opposite radially extending arms disposed adjacent to the front surface of said hammer and which hammer is characterized by a pair of diametrically opposite jaw members slidably mounted in its front end and normally spring urged to positions rearwardly of the front surface of the hammer,

.means for projecting said jaw members forwardly once during each revolution of the hammer relative to the anvil whereby to deliver impact blows to said anvil arms comprising, a series of three axially spaced cam plates disposed about the shank portion of said anvil member for axial movement relative thereto with the forwardmost plate being keyed to said hammer for rotation therewith and having its front face engageable with the rear ends of said jaw members, with the rearwardmost plate being connected to said anvil shank in a manner permitting limited relative rotation therebetween, and with the intermediate plate being freely rotatable relative to said anvil shank, and cam means associated with the adjacent faces of said three cam plates with said cam means of said forwardmost and intermediate cam plates co-acting once during each revolution of said hammer in one direction so as to project said forwardmost cam plate forwardly whereby to position said jaw members for delivering impact blows to corresponding anvil arms and with said cam means of said intermediate and rearwardmost cam plates co-acting once during each revolution of said hammer in the opposite direction so as to project both said forwardmost and intermediate cam plates forwardly whereby to position said jaw members for delivering impact blows to said anvil arms.

3. In a rotary impact tool of the type having a generally cylindrical hammer adapted to be rotatably driven by reversible rotary accelerating means, an elongated anvil including a shank portion extending co-axially through said said hammer and being rotatable relative thereto which anvil is characterized by a pair of diametrically opposite radially extending arms disposed adjacent to the front surface of said hammer and which hammer is characterized by a pair of diametrically opposite jaw members slidably mounted in its front end and normally spring urged to positions rearwardly of the front surface of the hammer, means for projecting said jaw members forwardly once during each revolution of the hammer relative to the anvil whereby to deliver impact blows to said anvil arms comprising, a series of three axially spaced 13 plates disposed about the shank portion of said anvil member for axial movement relative thereto with the forwardmost plate being keyed to said hammer for rotation therewith and having its front face engageable with the rear ends of said jaw members, with the rearwardrnost plate being connected to said anvil shank in a manner permitting limited relative rotation therebetween, and with the intermediate plate being freely rotatable relative to said anvil shank, and a pair of ramp-like cam members formed on each face of said three plates which is adjacent to a face of another of said plates, said cam members each terminating at its high point at an end surface which extends axially of the hammer and anvil, said cam members being arranged and being adapted to co-act in a manner whereby during clockwise rotation of said hammer said intermedfate and forwardmost plates are operably keyed together with both said intermediate and forwardmost plates being cammed forwardly once during each revolution of said hammer to project said jaw members into their forwardmost positions for delivering impact blows to corresponding said anvil arms and whereby during counterclockwise rotation of said hammer said intermediate and rearwardmost plates are operably keyed to- .gether with said forwardmost plate being cammed forvwardly once during each revolution of said hammer to project said jaw members into their forwardrnost positions for delivering impact blows to said anvil arms.

4. In a rotary impact tool of the type having a generally cylindrical hammer adapted to be rotatably driven by reversible rotary accelerating means, an elongated anvil including a shank portion extending co-axially through said hammer and being rotatable relative thereto, which anvil is characterized by a pair of diametrically opposite radially extending arms disposed adjacent to the front surface of said hammer and which hammer is characterized by a pair of diametrically opposite jaw members slidably mounted in its front end and normally spring urged to positions rearwardly of the front surface of the hammer, means for projecting said jaw members forwardly once during each revolution of the hammer relative to the anvil whereby to deliver impact blows to said anvil arms comprising, a series of three axially spaced cam plates disposed about the shank portion of said anvil member for axial movement relative thereto with the forwardmost plate be'ng keyed to said hammer for rotation therewith and having its front face engageable with the rear ends of said jaw members, with the rearwardrnost plate being connected to said anvil shank in a manner permitting limited relative rotation therebetween, and with the intermediate plate being freely rotatable relative to said anvil shank, a pair of circumferentially and radially spaced inclined ramp members projecting outwardly from each face of said intermediate plate, and a pair of mating inclined ramp members projecting forwardly and rearwardly, respectively, from the front face of said rearwardmost cam plate and from the rear face of said forwardmost cam plate, said ramp members each terminating at its high point at an end surface which extends axially of the hammer and anvil, whereby during rotation of the hammer in one direction said ramp members on the rear face of the forwardmost plate are engageable with said ramp members on the front face of the intermediate plate and said end surfaces on the rear face of the intermediate cam plate but said end surfaces of said rearwardmost cam plate whereby the forwardmost plate is cammed in a forward direction to project said jaw members into positions for delivering impact blows to corresponding anvil arms and whereby during rotation of the hammer in the opposite direction said ramp members on the front face of the rearward-most plate are engageable with said ramp members on the rear face of the intermediate plate and said end surfaces on the front face of the intermediate cam plate abut said end surfaces on said forwardmost cam plate whereby both the intermediate and forwardmost plates are cammed in a forward direction to project said 14 jaw members into positions for delivering impact blows to the opposite side edges of said pair of anvil arms.

5. In a rotary impact tool of the type having a generally cylindrical hammer member adapted to be rotatably driven by rotary accelerating means, an elongted anvil including a shank portion extending co-axially through said hammer and being rotatable relative thereto, which anvil is characterized by a pair of diametrically opposite radially extending arms disposed adjacent to the front surface of said hammer and which hammer is characterized by a pair of diametrically opposite jaw members slidably mounted in its front end and normally spring urged to positions rearwardly of the front surface of the hammer, means for projecting said jaw members forwardly once during each revolution of the hammer whereby to deliver impact blows to the side edges of said anvil arms comprising, a series of three axially spaced cam plates disposed about the shank portion of said anvil member for axial movement relative thereto with the forwardmost plate being keyed to said hammer for rotation therewith and having its front face engageable with rear ends of said jaw members, with the rearwardmost plate being connected to said anvil shank in a manner permitting limited relative rotation therebetween, and with the intermediate piate being freely rotatable relative to said anvil shank, a pair of circumferentially and radially spaced inclined ramp members projecting outwardly from each face of said intermediate plate, and a pair of mating inclined ramp members projecting forwardly and rearwardly, respectively, from the front face of said rearwardmost cam plate and from the rear face of said forwardmost cam plate, whereby during rotation of the hammer in one direction said ramp members on the front face of the rearwardmost plate are engageable with said ramp members on the rear face of the intermediate plate in a manner whereby both the intermediate and the forwardmost plates are carnmed in a forward direction to project said jaw members into positions for delivering impact blows to the opposite side edges of said pair of anvil arms, said forwardmost plate having on the rear face thereof a plurality of circumferentially spaced depressions for increasing frictional engagement between said forwardmost plate and said intermediate plate, said intermediate plate having on the front face thereof a plurality of circumferentially spaced depressions for increasing frictional engagement between said spacer plate and said forwardmost plate, whereby during rebound of said hammer after an impact blow has been delivered to said anvil relative rotary movement between said forwardmost plate and said intermediate plate will be restrained.

6. In a rotary impact tool of the type having a generally cylindrical hammer adapted to be rotatably driven by rotary accelerating means, an elongated anvil including a shank portion extending co-axially through said hammer and being rotatable relative thereto, which anvil is characterized by a pair of diametrically opposite radially extending arms disposed adjacent to the front surface of said hammer and which hammer is characterized by a pair of diametrically opposite jaw members slidably mounted in its front end and normally spring urged to positions rearwardly of the front surface of the hammer, means for projecting said jaw members forwardly once during each revolution of the hammer whereby to deliver impact blows to the side edges of said anvil arms comprising, a series of three axially spaced cam plates disposed about the shank portion of said anvil member for axial movement relative thereto with the forward-most plate being keyed to said hammer for rotation therewith and having its front face engageable with the rear ends of said jaw members, with the rearwardmost plate being connected to said anvil shank in a manner permitting limited relative rotation therebetween, and with the intermediate plate being freely rotatable relative to said anvil shank, a pair of circumferentially and radially spaced inclined ramp members projecting outwardly from each face of said intermediate plate, and a pair of mating inclined ramp members projecting forwardly and rearwardly, respectively, from the front face of said rearwardmost cam plate and from the rear face of said forward-most cam plate, whereby during rotation of the hammer in one direction said ramp members on the front face of the rearwardmost plate are engageable with said ramp members on the rear face of the intermediate plate in a manner whereby both the intermediate and forwardmost plates are cammed together in a forward direction to project said jaw members into positions for delivering impact blows to the opposite side edges of said pair of anvil arms, said forwardmost cam plate having on the rear face thereof a pair of circumferentially and radially spaced depressions adapted to receive, respectively, the outermost projecting portion of the inclined ramp members on the front face of said intermediate plate, said intermediate plate having on the front face thereof a pair of circumferentially and radially spaced depressions adapted to receive, respectively, the outermost projecting portion of the inclined ramp members on said forwardmost cam plate, whereby during rebound of said hammer after an impact blow has been delivered to said anvil relative rotary movement between said forwardmost cam plate and said intermediate plate will be restrained.

7. In an impact clutch of the type having a rotatable and a coaxially arranged cylindrical hammer rotatable with and relative to the anvil, which anvil includes diametrically opposite arms disposed adjacent the front of said hammer, said hammer having a pair of diametrically opposite jaws mounted in its front portion for sliding movement axially of the hammer, spring mean urging said jaws into a rearward position wherein the jaws clear the anvil arms, the improvement which comprises, cam means operated by relative rotary movement between the hammer and the anvil for forcing the jaws forwardly for impacting engagement with the anvil arms, said cam means including two sets of (so-operating cam members, one set of cam members acting during rotation of the hammer in one direction relative to the anvil to force the jaws forwardly and the other set of cam members acting during rotation of the hammer in the other direction relative to the anvil to force the jaws forwardly.

8. In .an impact clutch of the type having a rotatable anvil and a coaxially arranged cylindrical hammer rotatable with and relative to the anvil, which anvil includes diametrically opposite arms disposed adjacent the front of said hammer, said hammer having a pair of diametrically opposite jaws mounted in its front portion for sliding movement axially of the hammer, spring means urging said jaws into a rearward position wherein the jaws clear the anvil arms, the improvement which comprises, cam means operated by relative rotary movement between the hammer and the anvil for forcing the jaws forwardly for impacting engagement with the anvil arms, said cam means including three cam plates arranged in series axially of the anvil, said cam plates having cam members on their confronting faces thereby defining two sets of cam members, each cam member including an incline surface rising from the face of the associated cam plate and joining at its high point with a surface normal to the face of the associated cam plate, one set of cam members acting upon rotation of the hammer in one direction relativeto the anvil to carn one of the cam plate forwardly for forcing the jaws forwardly and the other set of cam members acting upon rotation of the hammer in the other direction relative to the anvil to cam said one cam plate and another cam plate forwardly for forcing the jaws forwardly.

9. In an impact clutch of the type having a cylindrical rotatable hammer with an axially extending central opening therein, an anvil extending eoaxially into said opening, which anvil includes diametrically opposite arms disposed adjacent the front of said hammer, the improvement which comprises, said hammer having a pair of diametrically opposite jaw pins mounted therein for sliding movement axially of the hammer, a pair of coil springs encircling said jaw pins, respectively, for urging the latter to a rearward position wherein the jaw pins clear the anvil arms, and cam means wholly contained within the hammer and operated by relative movement between the latter and the anvil for forcing the jaw pins forwardly for impacting engagement with the anvil arms.

References (Iited by the Examiner UNITED STATES PATENTS 2,563,711 8/1951 Fitch 192-305 2,784,818 3/1957 Maurer 19230.5 2,836,272 5/1958 Kaman 19230.5 3,106,274 10/1963 Madsen 19230.5

DON A. WAITE, Primary Examiner.

DAVID J. WILLIAMOWS-KY, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,228,486 January 11, 1966 Frank A. Kaman et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 49, for "of", first occurrence, read to column 4, line 72, for "acceleration" read accelerating column 5, line 4, for "reaction" read retraction line 10, for "calm" read cam line 48, for "real" read rear same column 5, line 53, after "along" insert the column 13, line 21, strike out "said"; line 64, for "but' read abut column 15, line 27, before "and" insert anvil Signed and sealed this 13th day of .December 1966.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Commissioner of Patents Attesting Officer 

1. IN A ROTARY IMPACT TOOL OF THE TYPE HAVING A GENERALLY CYLINDRICAL HAMMER ADAPTED TO BE ROTATABLY DRIVEN BY REVERSIBLE ROTARY ACCELERATING MEANS, AN ELONGATED ANVIL INCLUDING A SHANK PORTION EXTENDING CO-AXIALLY THROUGH SAID HAMMER AND BEING ROTATABLY RELATIVE THERETO, WHICH ANVIL IS CHARACTERIZED BY A PAIR OF DIAMETRICALLY OPPOSITE RADIALLY EXTENDING ARMS DISPOSED ADJACENT TO THE FRONT SURFACE OF SAID HAMMER AND WHICH HAMMER IS CHARACTERIZED BY A PAIR OF DIAMETRICALLY OPPOSITE JAW MEMBERS SLIDABLY MOUNTED IN ITS FRONT END AND NORMALLY SPRING URGED TO POSITIONS REARWARDLY OF THE FRONT SURFACES OF THE HAMMER, MEANS FOR PROJECTING SAID JAW MEMBERS FORWARDLY ONCE DURING EACH REVOLUTION OF THE HAMMER RELATIVE TO THE ANVIL THEREBY TO DELIVER IMPACT BLOWS TO SAID ANVIL ARMS COMPRISING, A PLATE MEMBER ROTATABLY MOUNTED ON THE SHANK PORTION OF SAID ANVIL MEMBER AND KEYED TO SAID HAMMER FOR ROTATION THEREWITH, SAID PLATE MEMBER HAVING ITS FORWARD FACE ENGAGEABLE WITH THE REAR ENDS OF SAID PAIR OF JAW MEMBERS AND BEING MOUNTED FOR MOVEMENT AXIALLY OF SAID HAMMER AND SAID ANVIL MEMBER, AND CAM MEANS ROTATABLE WITH AND RELATIVE TO SAID HAMMER FOR SHIFTING SAID PLATE MEMBER FORWARDLY WHEREBY TO PROJECT SAID JAW MEMBERS FORWARDLY INTO POSITIONS FOR DELIVERING IMPACT BLOWS TO SAID ANVIL ARMS ONCE DURING EACH REVOLUTION OF SAID HAMMER, SAID CAM MEANS INCLUDING FIRST AND SECOND COOPERATING CAMS EACH OF WHICH INCLUDES A RAMP 